Feeding mechanism in a sewing machine

ABSTRACT

A feeding module in the base on an electronic mechanical sewing machine is driven by an input shaft having two cam surfaces, one of which is arranged to drive a guide element in an oscillating movement. A block journalled on a shaft secured to a slide is displaceable in the guide by a mechanical or computer controlled electrical setting device. The slide is journalled in the feeder and displaceable perpendicularly to the working surface of the feeder. Upon a displacement of the slide the block will move into a corresponding position in the guide thereby effecting an adjustment of the feeding. The other cam surface is arranged to act upon a link connected to the transferring device to the feeder and is coordinated with the cam surfaces to guide the feeder in rectangular movements.

This invention is related to sewing machines, more particularly to thefeeding mechanism in the base of the sewing machine.

Problems caused by large size and large numbers of elements having anumber of points at which play occurs are usual in the feedingmechanisms of most sewing machines. Large distances for transferringactions and elastically in links, and the like, lead to inaccuracy whichis impossible to adjust. With regard to the assembly, it isunsatisfactory that a plurality of details must be inserted and adjusteddirectly in the body of the machine. An alternative to this is theassembly of the whole mechanism into a feeding module outside themachine and putting it into place without any time-consumingadjustments. When something is wrong with such a module it can easily betaken out of the machine to be mended or changed.

By the present invention it is presented a compact loop-taker andfeeding module which essentially reduces the problems occurring infeeding mechanisms as above discussed. The small number of elements ofthe module and its smallness make a reduction of the number of points ofplay as well as of the elasticity of the system. Due to the fact thatthe shuttle mechanism is also in the module two functions of the machineaccording to the invention are gathered in one module. This leads tostill another simplification of the work of adjustment in that themutual time-setting of the hook and the feeder is carried out whenassembling the module, after which the feeder and the hook follow inunison all time-settings of other instrumentalities in the machine. Theproblem of simplifying the assembling and adjustment of the hook andfeeder mechanism is solved according to the invention in that the driveand adjustment means of the feeder are located in a frame which by meansof fixing and adjusting points is applied to the base portion of thesewing machine.

An embodiment of a mechanism according to the invention is described byway of example in the following with reference to the accompanyingdrawing in which in FIG. 1 is a view of a mechanism according to theinvention in perspective, FIG. 2 is an exploded sketch of the mechanism,FIG. 3 is a vertical projection of the same and FIGS. 4a and 4b arecross sections of a level control member of a feeder showing a feedingposition (a) and a lowered position (b).

The hook- and feeder mechanism module in accordance with the inventionhas a base plate 10 with screw holes 11 for screws (not shown) forholding the module in corresponding holes in the machine body (notshown) of the sewing machine. A vertical main shaft 13 is secured to theplate 10 (FIG. 2) and a toothed wheel 14, the wheel 14 being driven by atransmission belt 15 from the motor not shown of the machine. A mitregear 16 journalled on the shaft and secured to the toothed wheel 14meshes with a corresponding gear 17 (FIG. 3) on a horizontal hook shaft18 which is also secured to the plate 10. The gears 16, 17 step up ofthe rotations so that the hook has double the r.p.m. as the toothedwheel 14. A hook carrier 19 journalled on the hook shaft drives the hook20 (FIG. 1) in rotating movement in the vicinity of the lower endposition of the needle. The top of the mechanism is covered by a stitchplate 21 (FIG. 2) sunk in the working surface (not shown) of the sewingmachine and can be lifted away so that the mechanism becomes visible. Onthe underside of the stitch plate a couple of pins 23, 24 protrude, anda feeder 25 is journalled on pins 23, 24, by means of a couple slots 26,27 extended in the material feeding direction. The feeder is plateshaped, having with a couple of stand-up rows of feeding teeth 28, 29which protrude in a couple of slots 30, 31 in the stitch plate. Due tothe guidance of elements 23, 26 and 24, 27 the rows of teeth 28, 29 movefreely in the slots 30, 31 when they make a feeding movement.

The feeder 25 is controlled to have a rectangularly shaped feedingmovement, in which the horizontal part of the movement is adjustable.The driving of the feeding movement is controlled by the gear 16 whichon its top surface has a couple of cam surfaces 32, 33, the surface 32being eccentric and the surface 33 having an axial curve. The eccentricsurface 32 controls a slide 34 journalled in the plate 10 anddisplaceable in its longitudinal direction transverse to the directionof material movement. A cam follower 35 on the slide 34 is in contactwith the eccentric surface 32 so that the slide 34 is forced away fromthe shaft 13 when the cam rotates. The slide is moved in the oppositedirection by a spring 36 located at a swingable guide 37, the guide 37being journalled on a shaft 38 on the plate 10 and joined to the slideby means of a pin 39 on the slide. The guide will then make anoscillating movement when the gear 16 rotates. A block 40 is journalledand displaceable in the guide 37 so that it can be driven thereby in theoscillating movement. The movement of the block 40 is determined by itsposition in the guide. Thus when the block 40 is in the middle of theguide 37 the center of the block will stand still (shown position). Thedisplacement of the block in the guide is effected by an adjustingarrangement, in the shown embodiment driven by a stepping motor 41. Thismotor 41 has a pinion 42 driving a rack 43 in reciprocal movement independence on stepping pulses to the motor 41. Such stepping pulses areemitted by an electronic unit which is not here further described. Therack is extended to a slide 44 journalled in slots 45 in the feederplate 25 and joined to the rack by a pivot 46. This slide 44 is locatedabove the guide 37 and has a pin 47 protruding into a hole 48 in theblock 40. Thus, the block can be displaced in the guide by means of thestepping motor 41 which also holds the block in an adjusted position.When the block 40 is adjusted to a position out of the center of theguide it is forced by the guide to make a reciprocal movement in theworking direction of the feeder 25. The feeder plate is given thismovement due to the fact that the slide 44 is journalled in the slots 45of the feeder plate. The slide 44 can make this movement in the feedingdirection due to the pivot 46 without disengagement of the rack from thepinion. A leaf spring 49 presses on the rack and holds it in mesh withthe pinion.

The vertical movement of the feeder 25 is substantially constant inmagnitude and coordinated with the horizontal movement so that thepattern of the movements forms approximately a rectangle. The feeder 25is adequately long that only its fore end, where the rows of teeth arelocated, needs to make a vertical movement, to ensure that the rows ofteeth arise above and sink below the working surface during of thesewing machine the several phases of the feeding. The rear end of thefeeder 25 is pressed against the underside of the plate and slidesagainst it during the feeding movements. The raising of the feeder 25 isbrought about by the axial cam surface 33 which acts upon a lever arm 50pivoted on the base plate 10 the arm 50 having a cam follower 51. Whenthe cam surface 33 raises the arm 50, which it will do before the feeder25 starts to make the horizontal movement, because of the coordinationof the cam surfaces 32, 33, the arm raises the feeder 25 against theunderside of the stitch plate 21. When the horizontal movement iscomplete the feeder is lowered by means of a couple of springs 52, 53which always keep the feeder in contact with an externally operablemanual level control member 54 in turn connected to the arm 50. Thisarrangement is illustrated in FIGS. 4a and b showing the arrangement ina cross section. The level control member is in this embodimentconstituted of a bar 55 and an eccentric 56 on a shaft 57. Shaft 57 isjournalled in a couple of bearing brackets 58, 59 manually turnable bymeans of a knob 60. In one of the positions of the eccentric 56 (FIG.4a) the bar 55 is raised against a support 61 on the underside of thefeeder 25, and a lug 62 on the eccentric 56 forms a fulcrum of the barraised in its opposite end by the arm 50 which in its turn is actuatedby the axial cam surface 33. A vertical movement is this transferred tothe feeder plate 25. However, it can be disconnected so that the feedingdoes not take place for the reason that the rows of teeth 28, 29 aresunk below the stitch plate. This is brought about by turning theeccentric 56 to the other position (FIG. 4b) so that the lug 62 releasesthe bar 55 which then falls down to the arm 50 and thereby does notreach the support 61 during the movement of the arm. The springs 52, 53will then always keep the feeder plate in its lower position whereby thefeeding fails.

I claim:
 1. In a feeding mechanism for a sewing machine, the sewingmachine having a stitch plate and drive means, said feeding mechanismhaving a cloth feeder arranged below the stitch plate, first cam meansmoving the cloth feeder in a cloth feed direction and second cam meansfor moving the cloth feeder toward and away from said stitch plate, saidfirst and second cam means being driven by said drive means; theimprovement wherein said feeding mechanism further comprises a frame, aguide journalled on said frame about an axis substantially normal tosaid stitch plate, means coupled to said first cam means forreciprocably moving said guide, said first and second cam means beingjournalled to said frame, block means slidably mounted on said guide,slide means coupled to said block for moving said cloth feeder in saidfeed direction upon reciprocation of said guide, and adjustment meansfor moving said block means in a direction substantially perpendicularto said feed direction for adjusting the movement of said cloth feederin said feed direction.
 2. The feeding mechanism of claim 1 wherein saidframe is mounted below said stitch plate, said first and second cammeans being journalled on a shaft on said frame, and further comprisingtransmission means coupling said drive means of said sewing machine torotate said first and second cam means.
 3. The feeding mechanism ofclaim 2 wherein said transmission means comprises a transmission belt.4. The feeding mechanism of claim 2 wherein said guide is journalled ona second shaft on said frame and parallel to said first-mentioned shaft.5. The feeding mechanism of claim 1 wherein said means coupling saidfirst cam means for reciprocably moving said guide comprises aconnecting link.
 6. The feeding mechanism of claim 1 wherein lever meansare provided for moving said cloth feeder toward and away from saidstitch plate by said second cam means.
 7. The feeding mechanism of claim1 wherein said cloth feeder comprises a plate mounted below said stitchplate and having rows of teeth extending therefrom toward said stitchplate.
 8. The feeding mechanism of claim 7 wherein said plate formingsaid cloth feeder is mounted to be movable in said feed direction andone end thereof is pivoted about an axis parallel to said feed directionfor permitting movement of said teeth toward and away from said stitchplate.
 9. The feeding mechanism of claim 1 wherein spring means areprovided for biasing said guide in one direction.
 10. The feedingmechanism of claim 1 further comprising a shaft affixed to said frameand extending perpendicular to said stitch plate, a toothed wheeljournalled on said shaft, a transmission belt coupling said drive meansto said toothed wheel, said first and second cam means being mounted forrotation with sad toothed wheel, said feeding mechanism furthercomprising a hook, and gear means driven by said toothed wheel forrotating said hook.